The present invention relates to sunken lawn sprinklers which are automatically projected or advanced to a position above the surrounding ground level when water pressure is applied to the sprinkler. In particular, the invention relates to a projectable guard which may be connected to such sprinklers to prevent foreign particles such as grass, leaves, sand, dirt, and the like from entering the portion of the housing beneath the boot.
Many parks and schools, athletic fields, golf courses, and residences are installing automatic irrigation systems to provide adequate moisture for landscaping and to maintain vast acres of lawn in a high degree of perfection. In such applications the pop-up type of sprinkler heads have been found most desirable to facilitate ground maintenance. Further, by using popup sprinkler heads which retract out of sight when not in use, the hazards associated with permanently elevated obstruction are eliminated. Such hazards include accidents incurred by tripping or falling over the sprinkler, striking the sprinkler with a lawnmower or automobile, and theft of a permanently elevated sprinkler head.
Many forms of projectable sprinklers have been proposed both commercially and in the patent literature. U.S. Pat. Nos. 4,010,901; 3,758,038; 3,104,822; 2,611,644; and 2,013,849 disclose various types of pressure operated pop-up sprinklers. By the term "pressure operated" is meant that the lawn sprinklers are projected up by the pressure of the water supplied to the sprinklers. Another method of raising or projecting a sprinkler is disclosed in U.S. Pat. Nos. 3,921,911 and 3,709,435 wherein the projectable lawn sprinklers float upward from the ground.
One difficulty encountered in making a sucessful pressure operated lawn sprinkler has been the complexity and number of parts required. Some sprinklers are costly to manufacture, difficult to assemble, repair and service, and are unreliable in operation. Furthermore, pressure operated pop-up sprinklers have suffered from the inability to seal well. Poor sealing causes an unnecessary large drop in pressure with the result that fewer projectable sprinklers than permanently raised sprinklers could be used on a supply line of given hydraulic capacity.
A further problem encountered in prior art projectable lawn sprinklers was that to prevent the stand pipe projected from the ground from rocking, it was necessary to have the relatively movable parts fit one another quite closely and to have lengthy bearing surfaces, i.e., lands. However, when the parts fit closely, natural friction develops and foreign matter tends to stick between the parts. This sometimes jams the stand pipe, and at other times scores the parts so as to permit leakage to develop. Furthermore, the use of long lands requires additional force to raise the stand pipe, and it is therefore more vulnerable to jamming.
From the above it can be seen that there is a need for a device and/or method for preventing sand, grass, leaves, dirt, and other foreign matter from entering the housing and jamming the moving parts.